This invention relates to ceramic coatings for the protection of the surfaces of substrates such as electronic devices like integrated circuits on semiconductor chips. The invention also relates to ceramic coatings used to form interlevel dielectric films to isolate metallization layers in electronic devices.
A common cause of failure of electronic devices is microcracks or voids in the surface passivation of the semiconductor chip allowing the introduction of impurities. Thus a need exists for improved protective coatings which will resist the formation of microcracks, voids or pinholes even during use in stressful environments.
Passivating coatings on electronic devices can provide barriers against ionic impurities, such as chloride ion (Cl.sup.-) and sodium ion (Na.sup.+), which can enter an electronic device and disrupt the transmission of electronic signals. The passivating coating can also be applied to electronic devices to provide some protection against moisture and volatile organic chemicals.
It is known to use planarizing interlayers within the body of an electronic device between the metallization layers. Gupta and Chin (Microelectronics Processing, Chapter 22, "Characteristics of Spin-On Glass Films as a Planarizing Dielectric", pp. 349-65, American Chemical Society, 1986) have shown multilevel interconnect systems with isolation of metallization levels by interlevel dielectric insulator layers of doped or undoped SiO.sub.2 glass films. Spin-on glass films have been utilized to provide interlayer isolation between the metallization layers, the top layer of which is later patterned by lithographic techniques.
Glasser et al. ("Effect Of The H.sub.2 O/TEOS Ratio Upon The Preparation And Nitridation of Silica Sol/Gel Films", Journal of Non-Crystalline Solids 63, (1984) p. 209-221) utilized solutions of hydrolyzed tetraethoxysilane (TEOS), and not hydrogen silsesquioxane resin, to produce silica sol/gel films which were subsequently subjected to thermal treatment and nitridation in an ammonia atmosphere. Glasser et al. suggests that the nitrided silica sol/gel films may be useful oxidation barriers for silicon and other metal surfaces.
Brown and Pantano, Journal of the American Ceramic Society, 70(1) pp. 9-14, 1987, discloses the thermochemical nitridation of microporous silica films in ammonia using so-called "sol gels" derived from tetraethoxysilane as the starting material. Brown and Pantano does not teach the use of hydrogen silsesquioxane resin as the starting material, nor does it teach the low temperature process claimed herein.
Rust et al., U.S. Pat. No. 3,061,587, issued Oct. 30, 1963, teaches a process for forming ordered organo silicon-aluminum oxide copolymers by reacting dialkyl diacyloxysilane or dialkyl dialkoxysilane, with trialkylsiloxy dialkoxy aluminum.
Frye and Collins teach in U.S. Pat. No. 3,615,272, issued Oct. 26, 1971, and also in Frye, et al., J. Am. Chem. Soc., 92, p. 5586, 1970, the formation of hydrogen silsesquioxane resin.
The inventors have recently filed several patent applications on inventions related to the formation of ceramic coatings for the protection of electronic devices. These patent applications include: Ser. No. 938,679, titled "Multilayer Ceramics From Silicate Esters", filed Dec. 4, 1986 in the names of Loren Haluska, Keith Michael, and Leo Tarhay; Ser. No. 937,274, titled "Multilayer Ceramics From Hydrogen Silsesquioxane", filed Dec. 3, 1986 in the names of Loren Haluska, Keith Michael, and Leo Tarhay; Ser. No. 937,276, titled "SiN-Containing Coatings For Electronic Devices", filed Dec. 3, 1986 in the names of Ronald Baney, Loren Haluska, Keith Michael, Sarah Snow, and Leo Tarhay; Ser. No. 937,273 titled "Platinum and Rhodium Catalysis of Low Temperature Formation Multilayer Ceramics", filed on Dec. 3, 1986 in the names of Loren Haluska, Keith Michael, and Leo Tarhay; Ser. No. 000,217, titled "Multilayer Ceramic Coatings From Silicate Esters and Metal Oxides", filed on Jan. 2, 1987 in the names of Loren Haluska, Keith Michael, and Leo Tarhay; Ser. No. 938,678, titled "Platinum or Rhodium Catalyzed Multilayer Ceramic Coatings From Hydrogen Silsesquioxane Resin and Metal Oxides", filed on Dec. 4, 1986 in the names of Loren Haluska, Keith Michael, and Leo Tarhay; and Ser. No. 938,677, titled "Multilayer Ceramic Coatings From Metal Oxides for Protection of Electronic Devices", filed on Dec. 4, 1986, in the names of Loren Haluska, Keith Michael, and Leo Tarhay.